I think this is a very good question and although many here state that 1 Million per Bitcoin is to much or mining will get more efficient etc it does not change the basic facts:
Miners will allways spend roughly the equivalent of the coins worth for mining. Because if they spend way less it would be so profitable that other will join up to the point where it isn't. A considerable portion of it will be spent for energy.
Energy consumption of the network already is quite huge and probably way more than would be neccessary (i'm no an expert there but it does not look reasonable).
Assuming bitcoin continues its considerable growth we don't have to wait until it hits a million. Each growth in value by factor ten will also be followed by a similiar growth of energy consumption. The question is does the block reward shrink fast enough to counter the growth in value?